| 1. |
- Einarsdottir, Ingibjörg, 1951, et al.
(författare)
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Atlantic halibut growth hormone: structure and plasma levels of sexually mature males and females during photoperiod-regulated annual cycles
- 2002
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Ingår i: General and Comparative Endocrinology. - 0016-6480 .- 1095-6840. ; 127:1, s. 94-104
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Tidskriftsartikel (refereegranskat)abstract
- The main objectives of this study were to obtain the amino acid sequence of Atlantic halibut (Hippoglossus hippoglossus) growth hormone (hhGH) and compare it with other teleost species, to establish a radioimmunoassay to assess plasma hhGH levels and thus to gain information about possible biological functions and regulation by photoperiod. The hhGH gene was cloned and its amino acid sequence deduced from the cDNA. The mature hhGH protein consists of 186 amino acids. Comparison with other flatfish species as well as a species from a different order, the pufferfish, reveals that the sequence similarities of the mature hhGH with that of the barfin flounder, the Japanese flounder, the sole and the pufferfish are 99.5, 81.7, 74.2, and 65.2%, respectively. The sequence similarities appear to correctly reflect the gross phylogenetic relationships among these telcost species. A specific GH-RIA was developed for measurements of Atlantic halibut GH levels. Assessment of plasma GH levels in adult halibut revealed large gender differences, with GH levels frequently being an order of magnitude higher in males than females. The mean (+/-SEM) plasma GH for males kept on normal annual photoperiod were 25.2 +/- 6.11 ng ml(-1) and for females were 5.14 +/- 1.94 ng ml(-1). It appears likely that plasma growth hormone levels in Atlantic halibut can be inversely correlated to growth and metabolism. Shifting of the annual photoperiod cycles demonstrated that photoperiod in not a regulator of plasma GH levels in the Atlantic halibut. but further research is needed to assess whether GH plays a role in the reproduction of this marine teleost species. (C) 2002 Elsevier Science (USA). All rights reserved.
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| 2. |
- Larsson, D. G. Joakim, 1969, et al.
(författare)
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Regulation of androgen receptors in Atlantic croaker brains by testosterone and estradiol.
- 2002
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Ingår i: General and comparative endocrinology. - 0016-6480. ; 128:3, s. 224-30
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Tidskriftsartikel (refereegranskat)abstract
- A nuclear androgen receptor (AR1), distinctly different from the mammalian AR, has previously been identified in the brain of the Atlantic croaker, Micropogonias undulatus. Interestingly, brain AR1 levels were higher in gonadally recrudesced than in regressed fish. Therefore, the possible involvement of gonadal steroids in the regulation of brain AR1 levels was investigated in the present study. Saturation analysis of [3H]testosterone binding showed that brain AR1 levels were significantly reduced (2-3-fold) in either the nuclear or cytosolic fractions of both males and females three weeks after gonadectomy. Implantation of gonadectomized females with testosterone or estradiol-17beta one week prior to sampling resulted in physiological plasma steroid concentrations and restored brain AR1 levels to 60-105% of those in intact or sham-operated fish. These results suggest that gonadal factors, including both androgens and estrogens, are involved in the physiological regulation of brain androgen receptors in a teleost species during the reproductive cycle.
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| 3. |
- von Hofsten, Jonas, et al.
(författare)
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Fushi tarazu factor-1 mRNA and protein is expressed in steroidogenic and cholesterol metabolising tissues during different life stages in Arctic char (Salvelinus alpinus)
- 2003
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Ingår i: General and Comparative Endocrinology. - : Elsevier. - 0016-6480 .- 1095-6840. ; 132:1, s. 96-102
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Tidskriftsartikel (refereegranskat)abstract
- Fushi tarazu factor-1 (FTZ-F1) genes belong to the nuclear receptor family 5A (NR5A). The distribution pattern of NR5A genes in teleosts suggests that they control functions separate to, or in addition to, those of other vertebrates. In mammals NR5A1 genes, including steroidogenic factor-1 (SF-1), are primarily involved in steroidogenesis. NR5A2 contain the alpha-fetoprotein transcription factor (FTF) genes, which protect mammalian embryos against maternal estrogens, and are involved in cholesterol transfer and metabolism. In this study we have analysed the expression of two Arctic char FTZ-F1 forms belonging to the NR5A2 group. The expression starts during early development and the transcripts are present in embryonic liver/pancreas and gonadal regions. The genes are up-regulated during embryogenesis as the embryo develops towards hatch, as shown by increased mRNA and protein levels. In adult Arctic char the FTZ-F1 forms are primarily located to tissues involved in steroidogenesis as well as cholesterol metabolism. Thus, a division of NR5A into SF-1 (NR5A1) and FTF (NR5A2) specific functions does not appear to have occurred in teleosts.
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| 4. |
- von Hofsten, Jonas, et al.
(författare)
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Fushi tarazu factor-1 mRNA and protein is expressed in steroidogenic and cholesterol metabolising tissues during different life stages in Arctic char (Salvelinus alpinus)
- 2003
-
Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 132:1, s. 96-102
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Tidskriftsartikel (refereegranskat)abstract
- Fushi tarazu factor-1 (FTZ-F1) genes belong to the nuclear receptor family 5A (NR5A). The distribution pattern of NR5A genes in teleosts suggests that they control functions separate to, or in addition to, those of other vertebrates. In mammals NR5A1 genes, including steroidogenic factor-1 (SF-1), are primarily involved in steroidogenesis. NR5A2 contain the alpha-fetoprotein transcription factor (FTF) genes, which protect mammalian embryos against maternal estrogens, and are involved in cholesterol transfer and metabolism. In this study we have analysed the expression of two Arctic char FTZ-F1 forms belonging to the NR5A2 group. The expression starts during early development and the transcripts are present in embryonic liver/pancreas and gonadal regions. The genes are up-regulated during embryogenesis as the embryo develops towards hatch, as shown by increased mRNA and protein levels. In adult Arctic char the FTZ-F1 forms are primarily located to tissues involved in steroidogenesis as well as cholesterol metabolism. Thus, a division of NR5A into SF-1 (NR5A1) and FTF (NR5A2) specific functions does not appear to have occurred in teleosts.
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| 5. |
- Anderson, WG, et al.
(författare)
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Purification, characterization, and biological activity of insulins from dogfish, Scyliohinus canicula, and the hammerhead shark, Sphyrna lewini.
- 2002
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 126:1, s. 113-122
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Tidskriftsartikel (refereegranskat)abstract
- Insulin was purified from pancreatic extracts of two elasmobranch species belonging to different families in the order Carcharhiniformes, the European spotted dogfish, Scyliorhinus canicula (Scyliorhinidae), and the hammerhead shark, Sphyrna lewini (Carcharhinidae). The amino acid sequence of dogfish insulin was established as A-chain GIVDHCCRNT(10) CSLYDLEGYC(20)NQ and B-chain LPSQHLCGSH(10)LVETLYFVCG(20)QKGFYYVPKV(30). The primary structure of hammerhead shark insulin was similar to that of dogfish insulin with only 2 amino acid substitutions at A8 (R --> H) and B30 (V --> I). The elasmobranch insulins were markedly different from human insulin (17 amino acid substitutions) but all the residues in human insulin that are believed to be important in determining the receptor binding conformation (B6, B8, B11, B13, B23, B24, B25, A2, A3, and A19) have been conserved in the elasmobranch insulins with the exception of the conservative substitution Phe --> Tyr at B25. Consistent with this, dogfish and human insulin showed almost identical binding affinity to the recombinant solubilized human insulin receptor (K-D values of 14.0 and 18.6 pM, respectively; relative potency 133%). Previous studies have shown that bovine insulin produces severe and sustained hypoglycemia in elasmobranchs but the effect is of slow onset. Bolus arterial injections of dogfish insulin (10 nmol (.) kg(-1)) into unanesthetized, fasting dogfish (n = 9) produced no changes in blood glucose, 3-hydroxybutyrate, and acetoacetate concentrations over a 4-h period. In a second series of experiments (n = 7), dogfish insulin (10 nmol (.) kg(-1)) produced a significant (P < 0.05) fall in blood glucose after 12 h that persisted for at least 48 h, but no change in ketone body concentrations. The data indicate that the metabolic actions of an endogenous elasmobranch insulin in an elasmobranch are similar to those previously described for mammalian insulin. (C) 2002 Elsevier Science (USA).
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| 6. |
- Berg, A. H., et al.
(författare)
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Regulation of Arctic char (Salvelinus alpinus) egg shell proteins and vitellogenin during reproduction and in response to 17β-estradiol and cortisol
- 2004
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Ingår i: General and Comparative Endocrinology. - : Elsevier. - 0016-6480 .- 1095-6840. ; 135:3, s. 276-285
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Tidskriftsartikel (refereegranskat)abstract
- Estrogens induce both vitellogenin (Vtg) and egg shell (zona pellucida; ZP) protein synthesis in salmonids. However, while Vtg is strictly under estrogenic control, recent reports suggest that additional mechanisms are involved in ZP protein synthesis. During sexual maturation both estrogen and glucocorticoid levels increase in the circulation of female fish. As glucocorticoids have been shown to interfere with Vtg induction in fish we investigated whether cortisol (F) had similar effects on ZP regulation. In the present study we determined both the natural variation in Vtg and ZP during an annual reproductive cycle in female Arctic char (Salvelinus alpinus), and the effect of co-treatment of juvenile Arctic char with 17β-estradiol (E2) and F. During sexual maturation the expression of Vtg and ZP correlated to plasma levels of E2 and F. Determination of Vtg and ZP protein levels following co-treatment with E2 and F showed that F antagonized E2 induction of Vtg. However, F was observed to potentiate the expression of ZP protein in the same fish. These results indicate that in Arctic char Vtg and ZP proteins are not regulated by the same mechanisms and suggest that ZP protein expression does not necessarily imply exposure to estrogenic compounds alone, and may thus not be ideally suited as a biomarker of exposure to estrogenic compounds.
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| 7. |
- Björnsson, Björn Thrandur, 1952, et al.
(författare)
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Photoperiod regulation of plasma growth hormone levels during induced smoltification of underyearling Atlantic salmon.
- 2000
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Ingår i: General and comparative endocrinology. - : Elsevier BV. - 0016-6480. ; 119:1, s. 17-25
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Tidskriftsartikel (refereegranskat)abstract
- Earlier studies have established that increased daylength increases plasma growth hormone (GH) levels during spring smoltification of yearling Atlantic salmon. Recently, the Atlantic salmon aquaculture industry has started the production of underyearling ("summer") smolts. This involves fast juvenile growth on continuous light (24L), the transfer of juveniles over 8 cm in length to short day (12L) for 6 weeks in the summer, followed by transfer to 24L for another 6 weeks before transfer to seawater in late October. Three groups were studied in fresh water from July to the following May in order to elucidate the GH response to this photoperiod manipulation: one group was kept on 24L throughout (long-day group), while the other two groups were exposed to short day from July 15th. Of these, one was brought back onto long day on September 1st (winter group) while the other was kept on short day (short-day group). Plasma GH levels of the long-day group were around 1.6 ng/ml throughout the study. The short-day transfer suppressed GH levels to 0.7 ng/ml within 2 weeks (short-day and winter groups). The long-day transfer (winter group) increased GH levels to 11 ng/ml within 3 weeks, and this elevation of GH levels was sustained for about 3 months, before declining to pretreatment levels. The study demonstrates that underyearling Atlantic salmon react to increased daylength in a way similar to traditional yearling smolts. It also demonstrates for the first time that decreased daylength can suppress plasma GH levels in fish. It is concluded that winter photoperiod manipulation causes an out-of-season initiation and completion of the parr-smolt transformation of underyearling Atlantic salmon and that growth hormone plays a major role in this process.
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| 8. |
- Elofsson, Ulf, et al.
(författare)
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Intermale competition in sexually mature arctic charr : effects on brain monoamines, endocrine stress responses, sex hormone levels, and behavior.
- 2000
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Ingår i: General and Comparative Endocrinology. - : Elsevier. - 0016-6480 .- 1095-6840. ; 118:3, s. 450-60
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Tidskriftsartikel (refereegranskat)abstract
- Sexually mature Arctic charr (Salvelinus alpinus) males were allowed to interact in pairs for 4 days in the absence of females. Agonistic behavior was quantified, and at the end of the experiment, plasma levels of glucose, cortisol, testosterone (T), 11-ketotestosterone (11-KT), and 17alpha,20beta-dihydroxy-4-pregnen-3-one (17alpha, 20beta-P) were determined alongside brain concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA, the major 5-HT metabolite), dopamine (DA), and 3,4-dihydroxyphenylacetic acid (DOPAC, a major DA metabolite). Plasma cortisol and glucose were significantly elevated in subordinate fish, and the number of aggressive acts received showed positive correlations with plasma levels of glucose on day 1, during the development of the dominance relationship, and of cortisol on day 4, when the dominance relationship was established. In contrast, plasma concentrations of T and 11-KT were significantly higher in dominant than in subordinate males, and there was a similar tendency in plasma concentrations of 17alpha,20beta-P. Further, plasma levels of these gonadal steroids were correlated with the number of aggressive acts performed on day 4, but not with the number of aggressive acts received. The plasma cortisol concentrations did not correlate with either 5-HIAA:5-HT or DOPAC:DA ratios in any of the brain parts analyzed. Plasma glucose levels showed positive correlations with brain 5-HIAA:5-HT ratios. Negative correlations were observed between 5-HIAA:5-HT ratios in the optic tectum and between plasma levels of T, 11-KT, and 17alpha,20beta-P. Telencephalic DOPAC/DA ratios displayed a negative correlation with plasma levels of T, 11-KT, and 17alpha,20beta-P, but only in dominant males.
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| 9. |
- Elofsson, Ulf OE, et al.
(författare)
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Intermale competition in sexually mature arctic charr: Effects on brain monoamines, endocrine stress responses, sex hormone levels, and behavior
- 2000
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Ingår i: GENERAL AND COMPARATIVE ENDOCRINOLOGY. - 0016-6480. ; 118:3, s. 450-460
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Tidskriftsartikel (refereegranskat)abstract
- Sexually mature Arctic charr (Salvelinus alpinus) males were allowed to interact in pairs for 4 days in the absence of females. Agonistic behavior was quantified, and at the end of the experiment, plasma levels of glucose, cortisol, testosterone (T), 11-k
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| 10. |
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